How to capture a string from the parameters of a url using regex expressions in javascript

Question

I've got a function that will display urls visited by users e.g. https://stackoverflow.com/questions/78/of/103/uk/ask

I want to use a regex expression with javascript to capture a specific parameter of the url and replace it with placeholder text. Taking the example above;

When https://stackoverflow.com/questions/7845w98439/uk/ask is matched, replace the '/78/of/103/uk/' part with '/task/of/total/country/'. The code below I have doesn't seem to work. Can someone show me where I'm going wrong?

JS:

const url_change = [
 {expression: '/^/78/of/103/uk//i', value: '/task/of/total/country/'}
];
const urlParam = url_change.reduce(function(result, item) {
 return element.classList.contains(item.expression) ? item.value : result;
 }, '');
return urlParam(
 toChange ? toChange.value : getElementText(element)
);

• georg: you have to escape all slashes in the regexp /^\/bla\/bleh etc

Answer 1

Do as follow:

var str = "https://stackoverflow.com/questions/78/of/103/uk/ask";
const url_change = [
 {expression: /\/78\/of\/103\/uk\//i, value: '/task/of/total/country/'}
];
// console.log(url_change[0].expression.test(str));
var result = str.replace(url_change[0].expression,url_change[0].value);
console.log(result);

Sign / is special character (announces the end of Regex expression), it needs a mark \ lead to become a / in url, for Regex expression!